In 3GPP (3rd Generation Partnership Project), which is a project aiming to standardize a mobile communication system, the specifications of a proximity service (ProSe: Proximity-based Services) have been designed.
Here, the ProSe includes a UE-to-Network relay in which a first radio terminal (ProSe UE-to-Network Relay) relays, between a second radio terminal (Remote UE) which is outside a network and the network, data (traffic) of the second radio terminal.